Method and device for cleaning fan impellers

ABSTRACT

In a method of cleaning fan impellers bursts of solid material are discharged towards the impeller blades or other parts of the impeller, subjected to deposits, by pulses of compressed air, shot from a compressed air cannon. A device for cleaning fan impellers includes at least one compressed air cannon for directing shots in the form of pulses of compressed air towards the impeller blades or other parts of the impeller. The outlet cylinder (280) of the cannon is loaded with a charge of solid material (4) to be discharged towards the impeller blades or said other parts of the impeller, upon shooting a pulse of compressed air.

TECHNICAL FIELD

The present invention relates to a method and a device for cleaning fanimpellers, said device comprising at least one compressed air cannon fordirecting shots in the form of pulses of compressed air towards theimpeller blades or other parts of the impeller, subjected to deposits.

BACKGROUND ART

In Swedish Patent Application No. 8902335-2 a method and a device isdescribed for producing a shock wave by means of a compressed air cannonto unstick deposits on fan impeller blades. This technique is applicableto fans used under heavy environment conditions, like in dusty spacessuch as in kilns of cement plants where deposits of dust on theimpellers can cause severe vibration problems. FIG. 1 shows an exampleof a device according to this prior art with a compressed air cannondisposed at the fan inlet.

In some applications the hardness of the deposits on the blade surfaceswill be so high that the deposits can not be efficiently removed bypulses of compressed air.

DISCLOSURE OF THE INVENTION

The purpose of the present invention is to improve the efficiency ofremoving such hard deposits from impeller blades or other parts of a fanimpeller.

This purpose is obtained by a method according to claim 1 and a deviceaccording to claim 6.

According to the invention hard deposits are removed by throwing burstsof solid material towards the impeller blades or other parts of theimpeller, subjected to deposits.

According to advantageous embodiments of the method according to theinvention the bursts of solid material are thrown periodically or arecontrolled as a function of the level of vibration of impeller bearings.

According to another advantageous embodiment of the method according tothe invention the bursts of solid material are thrown towardsdiametrically opposite blades of the impeller by means of two compressedair cannons to avoid excessive unbalance due to unsticking of thedeposits.

According to still another advantageous embodiment of the methodaccording to the invention the instant of shooting bursts of solidmaterial is controlled as a function of the blade positions of therotating impeller to provoke unsticking of deposits on the differentblades in a selected order to reduce the unbalance created by thisremoval of deposits.

According to an advantageous embodiment of the device according to theinvention the solid material is contained in a cylindrical cartridge,intended to be positioned in the outlet cylinder of the cannon, the endsof the cylindrical cartridge being closed by a material, brittle enoughto be broken by the compressed air pulse. Thus the cartridge has to beof sufficient strength to keep the material during transportation, whilethe ends of the cartridge has to be so brittle that it is broken, whenused in the air cannon, by the shot of compressed air from the cannon.

The solid material used is chosen according to the hardness of thedeposits and the fans liability to become damaged. The chosen solidmaterial must be of sufficient strength to crush the deposits and at thesame time be friable enough to eliminate the risk of damage or wearingof the impeller blades or other parts of the impeller. Thus, accordingto still another advantageous embodiment of the device according to theinvention, the solid material is formed of a coarse-grained material,the size of the grains being preferably between 5 and 50 mm, whichcoarse-grain material is friable without hard contents, and ispreferably formed of gypsum stones.

The solid material can also comprise an explosive which will explodewhen hitting the impeller blades or other parts of the impeller,subjected to deposits. With such a material a still more efficientcleaning effect can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplifying embodiment of the device according to the invention willnow be described more in detail with reference to the enclosed drawingson which

FIG. 1 shows an embodiment of a device of the type used in the presentinvention with a movable compressed air cannon located at the impellerinlet,

FIG. 2 in an axial section a portion of the outlet cylinder of the aircannon charged with a cartridge containing solid material,

FIG. 3 a cross-section through the plane 3--3 in FIG. 2, and

FIG. 4 a perspective view of the outlet cylinder of the air cannon withthe retainer cylinder for the cartridge partly swung out.

FIG. 1 shows a fan comprising an impeller 10 mounted inside a fan casingor fan scroll 18.

BEST MODE FOR CARRYING OUT THE INVENTION

A compressed air cannon 26 is located at the impeller inlet. The outletcylinder 28 of the cannon 26 can be oriented in the axial direction ofthe fan or in any inclined direction to deliver compressed air pulsestowards the impeller blades 24. The compressed air cannon which can beof the type described in the Swedish Patent Application 8902335-2 isshown in FIG. 1 in two different orientations.

A portion of the outlet cylinder 28 is shown in FIG. 2-4. A cartridge 2containing solid material 4 is placed in the bore of the outlet cylinder28.

The cartridge 2 is formed of a material of sufficient strength to keepthe material during transportation from being damaged. The ends of thecylinder are closed by a material 3 which is broken by the pressurepulse from the air cannon 26, such that the material 4 is thrown throughthe outlet cylinder 28 to hit the impeller blades 24 or possibly otherparts of the impeller subjected to deposits. The end walls 3 of thecartridge 2 can be formed e.g. of an expanded polystyrene composite orformed as cover plates of a thickness of up to 2 cm which plates arestuck with a proper adhesive to the cartridge cylinder. As anotherexemple the end walls 3 could be formed of paper of suitable quality.

The outlet cylinder 28 comprises a removable portion 5 in the form of ahalf cylinder in which a retainer cylinder 6 for the cartridge 2 ismounted. The half cylinder 5 is articuledly mounted by a hinge 30 to theremaining part of the outlet cylinder 28, such that the half cylinder 5can be swung along the hinge axis 8 out of the bore of the outletcylinder 28. In this way the retainer cylinder 6 mounted in the halfcylinder 5 can be removed from the bore of the outlet cylinder to allowremoval of used cartridges 2 and insertion of new ones containing thesolid material 4, whereupon the new cartridge 2 is swung into the boreof the outlet cylinder 28.

As a closing device for the movable half cylinder 5, a suitable clampingdevice 32 is used. A seal 7 is disposed between flanges 34 and 36 formedon the half cylinder 5 and the outlet cylinder 28 respectively to avoidair leakage with the half cylinder 5 positioned in the bore of theoutlet cylinder 28.

Other embodiments are possible for introducing the cartridges containingthe solid material into the bore of the outlet cylinder. Thus e.g. aconstruction with guide bars can be used to allow removal of theremovable portion from the outlet cylinder by a translational motion, ora revolver system can be associated with the outlet cylinder to allowloading of several cartridges.

The opening of the outlet cylinder to remove used cartridges andinserting new ones is not dangerous for the operator, even if the fan isoperating with hot gases. For such applications the fan is operating ata pressure below atmospheric pressure, and therefore when opening theoutlet cylinder air is flowing from the atmosphere into the fan. As aconsequence, the removable part of the outlet cylinder is then cleanedfrom dust and cooled rapidly.

The solid material 4 is a rather friable, coarse-grained material with atypical grain size of 5 to 50 mm. The material is selected depending onthe application such that deposits are effectively crushed and thenblown away as a powder while the material is friable enough foreliminating any risk of damage or wear of the impeller blades. As anexemple gypsum stones can be used without any hard content that couldgive rise to wear.

The solid material can also be formed of an explosive which will explodewhen hitting the impeller blades or other parts of the impellersubjected to deposits.

I claim:
 1. A device for cleaning fan impellers (10) having blades,comprising:at least one compressed air cannon (26) having an aircylinder directing shots in the form of pulses of compressed air towardsone of the impeller blades (24) and other parts of the impeller,subjected to deposits, a charge of said solid material (4) which isloaded in the outlet cylinder and discharged from said outlet cylindertowards said one of the impeller blades (24) and said other parts of theimpeller subjected to deposits, a cylinder cartridge (2) located in saidoutlet cylinder (28) wherein upon shooting a pulse of compressed airthrough said outlet cylinder, the solid material (4) is contained insaid cylindrical cartridge (2) and wherein ends of the cylindricalcartridge are at least partially enclosed by a material (3) brittleenough to be broken by the compressed air pulse.
 2. The device accordingto claim 1, wherein the material (3) which at least partially enclosesthe ends of the cylindrical cartridge comprises an expanded polystyrenecomposite.
 3. A device for cleaning fan impellers (10), comprising:atleast one compressed air cannon (26) having an air cylinder directingshots in the form of pulses of compressed air towards one of theimpeller blades (24) and other parts of the impeller, subjected todeposits, a charge of solid material which is loaded in the outletcylinder and discharged from said outlet cylinder towards the impellerblades (24) and said other parts of the impeller subjected to deposits,a cylinder cartridge (2) located in said outlet cylinders (28) whereinupon shooting a pulse of compressed air through said outlet cylinder,the solid material (4) is contained in said cylindrical cartridge (2)and wherein the ends of the cylindrical cartridge (2) are covered byplates which are connected to the cylindrical cartridge.
 4. The deviceaccording to claims 1 or 2 , wherein the outlet cylinder (28) of the aircannon (26) comprises a removable portion (5) allowing insertion of thecartridge (2) containing the solid material (4) into the outlet cylinderof the air cannon.
 5. The device according to claim 4, which comprises ahinge wherein the removable portion (5) of the outlet cylinder (28) ismounted to the remaining part of the outlet cylinder by said hinge (30)allowing said removable portion to be swung out of the bore of theoutlet cylinder along an axis (8) parallel to the axis of the outletcylinder.
 6. The device according to claims 1 or 2, wherein the solidmaterial (4) is formed of a coarse-grained material, and wherein thegrains are of a size between 5 and 50 mm.
 7. The device according toclaim 6, wherein the coarse-grained material comprises a friablematerial without hard contents.
 8. The device according to claims 1 or2, wherein the solid material (4) comprises an explosive which explodesupon hitting said one of the impeller blades (24) and other parts of theimpeller (10).
 9. The device according to claim 7, wherein said friablematerial comprises gypsum stones.